This invention relates to an electric fuel pump which is installed within a fuel tank of e.g. a motor vehicle, and pressure-supplies fuel to the engine, and more particularly to an electric fuel pump with a characteristic of low noise and high efficiency.
FIGS. 4 and 5 are a partially enlarged perspective view of an impeller and an enlarged perspective view of the vicinity of a radial sealing portion of a pump base of a conventional electric fuel pump disclosed in e.g. Japanese Patent Public. No. 63-63756, respectively.
In the figures, reference numeral 10 denotes an impeller equipped with a number of vanes 21 on the outer periphery of a disk shape. Each vane is divided into a front and rear segments by a partition 22. A vane groove 23 is formed between the respective vanes 21. Reference numeral 9 denotes a pump base constituting a pump casing (not shown) which includes an arc belt-shaped pump flowpath 13, a sucking inlet 4, a discharge outlet 15, a radial sealing portion 9a for preventing the backflow of the fuel and an end face 9b which converts the direction of flowing of the fuel.
When the impeller 10 rotates within the pump casing (not shown), the fuel sucked from the sucking inlet 14 flows into each of the vane grooves 23, The fuel is passed through the pump flowpath 13 under kinetic energy from each of the vanes 21, and pressure-supplied to the discharge outlet 15. The fuel pressure-supplied to the discharge outlet 15 collides with the end face 9b of the radial sealing portion 9a formed at the end of the pump flowpath 13 and discharged from the discharge outlet 15 while it changes the direction.
In such a structure, the fuel supplied into the left and right vane grooves 23 divided into the front and rear portions by the partition 22 simultaneously collides with the end face 9b of the radial sealing portion 9a. This presents a problem of increasing noise due to the fuel collision.
An example of the measure for solving this problem is disclosed in FIGS. 6 and 7 of JP-A-159283. In the pump base 9 constituting the pump casing (not shown) of the illustrated structure, the end face 9b of the radial sealing portion 9a is given a step 9c so that the timing of fluid collision is displaced to reduce the noise. In addition, the outer periphery of the vane 21 is projected more outwardly than the outer periphery of the partition 22 so that a backflow area (area impeding the pumping operation) is prevented from being created just on top of the partition, thereby improving the pumping efficiency.
In recent years, the needs of reducing the operation noise and mileage have been enhanced. Correspondingly, as described above, the conventional electric fuel pumps have adopted the measures of changing the respective shapes of the impeller and pump base to reduce the operation noise and improve the pump efficiency. However, the pump base, which is generally made of aluminum die-casting from the point of view of dimensional accuracy and mechanical strength, has presented a problem of requiring a huge amount of cost to repair and manufacture a mold product. Further, it is desirable that in order to reduce the operating noise, the step 9c is given on both sides of the sucking inlet and discharge outlet of the pump casing. However, it was difficult to provide a pump casing having such a structure by molding.
This invention has been made in order to solve the above problems, and intends to provide an electric fuel pump which can reduce the noise during a pump operation and gives high pumping efficiency.
The electric fuel pump according to this invention comprises a disk-shaped impeller including a number of vanes (31) formed at its outer edge and projected circumferentially, partitions (32) extended between the vanes (31) and vane grooves (33) formed by the partitions (32) and the vanes (31) provided at the front and rear of the partitions (32); a motor section (3) for rotationally driving the impeller (30); and a pump casing (7) which houses the impeller (30), forms an arc belt-shaped pump flow path (13) extending along the outer edge of the impeller (30), and has a sucking inlet (14) at the one end of the pump flow path (30) and a discharge outlet (15) at the other end thereof, and is characterized in that each of the vanes (31) includes a vane segment (31A) on the side of the one end face of the impeller (30) and a vane segment (31B) on the side of the other end face of the impeller (30), the vane segment (31A) on the side of the one end face and the vane segment (31B) on the side of the other end face are staggered by a prescribed distance (d) circumferentially of the impeller (30), and in the vane segment (31A) on the side of the one end face and the vane segment (31B) on the side of the other end face, guiding faces (31a, 31b) are formed which extend from the sides of the one end face and the other end face of the impeller (30) to the outermost periphery of the impeller (30) to guide fuel; each of the partitions (32) has guiding faces (32a, 32b) which extend from the sides of the one end face and the other end face of the impeller (30) to guide the fuel; and each of the vane grooves (33) includes a groove segment (33A) formed by a guiding face (31b) which extends from the side of the one end face of the impeller (30) to the outermost periphery of the impeller (30) to guide the fuel and the vane segment (31A) on the side of the one end face of the impeller; a groove segment (33B) formed around the partition (32) where both guiding faces (32a, 32b) of the partition (32) are opposite to each other; and a groove segment (33C) formed by a guiding face (31a) which extends from the side of the other end face of the impeller (30) to the outermost periphery of the impeller (30) to guide the fuel and the vane segment (31B) on the side of the other end face.
In the electric fuel pump, an outermost peripheral face (32c) of the partition (32) is located more inwardly than the outermost peripheral face (31c) of the vane (31). In the electric fuel pump, the outermost periphery of each of the guiding faces (31a, 31b) is coincident with a center line of the impeller (30) in the direction of thickness.